The calorific value is about no B.T.U. per cub. ft., and one
volume is mixed with 1-13 of air in the engine, for which propor-
tions the valves must be designed. The Simplex engine (p. 701)
has been enlarged for blast-furnace gas, an example of 700 H.P.
being shewn at the Paris Exhibition of 1900, and Fig. 1021
illustrates a complete plant for the supply and treatment of the
gas, where A A are washers, B B condensers to eliminate moisture,
c c scrubbers to remove ammonia, and D p sawdust filters. The
holder E stores the purified gas, and passes it on to the engine F.
Natural gas is obtained in petroleum districts, and its compli-
cated composition is given by the following average:—
CH4 . .....
CO ..... ,
5 j- diluents.
loo'o parts by volume,
shewing a rick gas with but few non-combustibles.